Solvent refining of hydrocarbon oil



Oct. 4, 1938. B Y. McCARTY 2,132,359

SOLVENT REFINING OF HYDROCARBQN OIL Filed July 1'7, 1933 552mm XA/(kwrr 11v VEN TOR #6 ATTORNEY Patented Oct. 4, 1938 g UNITED STATES PATENT OFFICE SOLVENT REFINING 18F HYDROCARBON Bernard Y. McCarty, Beacon, N. Y., assignor to The Texas Company, New York, N. Y., a. corporation of Delaware Application my 11, 1933, Serial No. 680.687

4 Claims. (01. 196-13) This invention relates to a process 01' refining the ordinary methods of treating with a selective hydrocarbon oil, and more particularly to a solvent.

method of treating mineral oil with a selective Accordingly, my invention comprises effecting solvent having a selective solvent action as becounter-current treatment of the oil with a se- 5 tween difi'erent constituents of the oil. lective solvent in a treating zone throughout 5 The invention contemplates a method of treatwhich a graduated range of temperature is maining oil with a solvent liquid having selective actained. Advantageously, this comprises progrestion as between naphthenic and parailinic consively decreasing the temperature throughout the stituents of the oil wherein the temperature of treating zone from the point at which the rattreatment is varied over a substantial range of finate is removed to the point at which the ex- 10 temperature. The invention is particularly well tract is discharged from the zone. Thus, as the adapted to the treatment of lubricating oils with extraction proceeds the oil undergoing treatment a selective solvent for the production of optiis subjected to contact with solvent liquid at promum yields of lubricating oil having a high visgressively increasing temperature. In this way cosity index and other desirable qualities. the refined oil or railinate is removed from the 15 The method of my invention is particularly system at relatively high temperature under applicable to the treatment of oil with selective which conditions the solvent exerts very high solvents, such as furfural, nitrobenzene, sulphur solubility for constituents of naphthenic nature, dioxide, aniline and the like, all of which poswhile the extract is removed from the system at sess selective solvent action as between napha relatively low temperature and at which the 20 thenic and paraiiinic constituents of the oil, or, paraflinic constituents are substantially insoluin other words. as between relatively low and ble in the solvent liquid. relatively high viscosity index constituents. Reference will now be made to the figures of Solvents of the foregoing type have arelatively the accompanying drawing for the purpose 011 high solvent action upon the naphthenic condescribing the method of my invention in greater 5 stituents of the oil and a relatively low solvent detail. action upon the more parafiinic type of constitu- Referring to Figure 1, the oil which is to be ents. There is, however, no clear line of detreated, such as lubricating oil for example, is marcation as to the solubility of those constitudrawn from a source not shown by a pump I so ents lying intermediate between t a v y and introduced to a mixer 2 wherein the oil is high and relatively low viscosity index bodies of brought into contact with the solvent liquid, the oil. Co q y, when treating Oil with 3 comprising for example, furfural, accumulating selective solv n of the foregoing yp h X- from an intermediate point such as the mixer 9 tracted portion o t e O remaining dissolved in in the treating zone and containing oil relathe solvent after treatment may contain subtively rich in naphthenic constituents. 35 stantial amounts of constituents intermediate The mixer 2 may gomprjse a closed vessel proin character between the extract and the more vlded with tirring means a d l it a 1 Daraflihic portion 01 the Oil, and which y be through which either a cooling or heating meof considerable value as lubricating products. 1m may b d ted for th purpose of regu..

T e t a d portion may also include l D lating the temperature within the mixer to the 40 ciable amounts of relatively high viscosity index degree de ir d, I material due to the solubility of these constitu- From the mixer 2, the mixture of oil and ents in the solvent-extract mixture. solvent is conducted through a pipe 3 to a settler I have found that, by car ying out the 8 4 wherein the mixture is subjected to settling.

traction of oil with these selective solvents over Th ettling chamber may also be provided with 45 a graduated range of temperature, it is possible a coil as indicated through which a heating or to btain a more complete separation between cooling medium may be circulated for the purthe valuable and less valuable constituents of the pose of maintaining the proper degree of t oil and produce an extract which is substantially perature,

50 free from dissolved valuable constituents. At the As a result of the settling, an upper layer same time, by the method of my treatment, it is will be formed, comprising partially-refined oil, possible to produce a refined oil portion or rafand a lower layer, comprising the solvent and finate, having superior qualities as regards visdissolved oil or extract. The lower layer now cosity index, for example, over that obtained by rich in extract is removed from the bottom oi 56 this settling chamber through a pipe I, and the solvent recovered therefrom for reuse.

The refined oil accumulating in the upper portion of the settler is conducted through a pipe 6 to a mixer I similar to the mixer 2, already described. This partially-refined oil is here mixed with solvent liquid collecting at the point of raillnate discharge at the settler I! in the treating zone and relatively lean in dissol ed constituents.

From the mixer 1, the mixture of solvent and oil is discharged through a pipe 8 into a settling chamber 8 similar to that already described, and wherein the oil, while at a relatively higher temperature, is subjected to settling.

The bottom layer accumulating in the settler 9, comprising solvent and dissolved oil constituents, is returned to the mixer 2, as already described, for treatment with fresh charge.

The upper layer, comprising relatively more refined oil, is drawn off through a pipe ill to a mixer ll, wherein it is mixed with fresh or recovered solvent liquid. The resulting mixture is then conducted through a pipe l2 to a final settling chamber [3, wherein the mixture is settled at a still higher temperature. The solvent and dissolved constituents forming the bottom layer in this settling chamber are returned to the mixer I, already referred to, while the refined oil or raiiinate. comprising the upper layer, is withdrawn from the system. Such solvent as remains mixed with the rafilnate may be recovered for reuse.

When treating lubricating oil stock, corresponding for example to an oil of 60 or Saybolt Universal viscosity at 210 F. with a solvent comprising furfural, temperatures throughout the treating zone may range from 130 or 150 F. at the extract end of the zone, to about 225 or 300 F. at the rafllnate end. Thus, the oil and solvent mixture in the settler 4 may be maintained at a temperature of 150, that in settler 9 at a temperature of 180 F., while that in the final settler 13 may be maintained at a temperature of around 225 F.

The proportion of solvent to oil used may be varied as desired, but will usually be about one or two parts of solvent to one part of oil.

Instead of employing a series of three or more mixing and settling units, as illustrated in Figure l, a vertical column type of treating system may be employed, such as illustrated in Figure 2.

As shown in Figure 2, the treating apparatus comprises a vertical tower IT. This tower is provided with nests of packing material l8, as indicated. This packing material may comprise Raschig rings, tile, or other suitable packing mate'rial. Instead of packing material of this type, bubble trays may be used, alternately arranged baffles, or sections of screen.

The raw untreated oil is introduced to the bottom of the tower through a pipe I9, terminating in a distributing head 20 located in the bottom of the tower.

The solvent is introduced to the top of the tower through a pipe 2| terminating in a similar distributing head 22 within the top of the tower. The refined oil or railinate is withdrawn through a pipe 23 from the top of the tower advantageously at a point above the distributing head 22, while the extract portion with the bulk of the solvent is withdrawn from the bottom of the tower through a pipe 24.

In practicing the invention with the tower type of treating zone, I have found it of advantage to produce the desired temperature diflerential within the tower by introducing the oil to the bottom of the tower at a low temperature, for example, at around or F., while introducing the solvent to the top of the tower in a heated condition, for example, at a temperature of around 250 or 300 F. The oil can, of course, be introduced at much lower temperature, as for example, around 0 F. or lower. In this way, there is a progressive decrease in the temperature of the liquid throughout the tower and towards the bottom, at which point the bulk of the solvent and extract material is being removed. The temperatures actually employed will depend of course upon the particular selective solvent being used.

If a selectivesolvent such as acetone is used and which is of lighter gravity than the oil being treated, then the flow through the treating tower may be reversed, so that the solvent is introduced to the bottom of the tower while the oil is introduced at the top.

The employment of a high temperature at the raflinate end of the treating zone results in an increase in the gravity and viscosity index of the refined oil. At high temperatures, the solvent has a high solvent effect upon the naphthenic as well as upon the more paraflinic or intermediate constituents. On the other hand, by maintaining a low temperature at the extract end of the treating zone, substantially no parailinic or intermediate constituents remain dissolved in the solvent due to their lower solubility in the solvent at the relatively lower temperatures prevailing therein. In this way, there results an increase in the yield of refined oil together with an appreciable increase in viscosity index.

While, in the foregoing example, treatment of lubricating oil with furfural as the selective solvent has been described, it is contemplated that the invention is adapted to the treatment of other types of hydrocarbon oil and also with selective solvents other than furfural. This method of treatment may be employed with such other mineral oil fractions as naphtha or kerosene, etc., or it may be used in treating waxbearing oils, or oils derived from distillate or residual sources.

It is also contemplated that, in many instances, it may be desirable to employ a less selective, modifying solvent liquid in admixture with the selective solvent liquid. As already indicated, the selective solvents other than furfural may comprise nitrobenzene, liquid sulphur dioxide, aniline, etc. Suitable modifying solvents which may be employed in admixture with these solvent liquids may comprise the homologs of benzene, such as benzol and toluol. When using a modifying solvent, such as benzol, it may be mixed with the selective solvent in the proportion desired, and the resulting solvent liquid mixture employed in the same manner as when using an undiluted selective solvent, as described above. The use of a suitable modifying solvent permits effecting the desired degree of extraction with relatively less of the selective solvent liquid.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In the countercurrent extraction of hydrocarbon oil with a selective solvent to form ramnate and extract phases respectively rich in parafllnic and non-paraflinic constituents and wherein the oil and solvent move countercurrently through an extraction zone, the steps comprising introducing the solvent at a temperature at which it exerts substantially complete solvent action on the non-paraihnic constituents of the oil to said extraction zone at a point adiacent the point of rafllnate phase discharge therefrom, and introducing the feed oil to said zone at a point more remote from the point of raflinate phase discharge and at a temperature substantially below that of the entering solvent such that a temperature differential of around F. or more is maintained within said zone between the points of solvent and oil introduction.

2. The method according to claim 1 in which the selective solvent comprises furfural.

3. In the countercurrent extraction of hydrocarbon oil with a selective solvent to form raffinate and extract phases respectively rich in parafilnic and non-paraflinic constituents and wherein the oil and solvent move countercurrently through an extraction zone, the steps comprising introducing a solvent comprising turfural at a temperature around 225 to 300 1'. to said zone at a point adJacent the point of raffinate phase discharge therefrom, and introducing the feed oil at a temperature of around to F. to said zone at a point more remote from the point 01 raflinate phase discharge such that a substantially large temperature differential is maintained within said zone between the points of solvent and oil introduction.

4. In the countercurrent extraction of hydrocarbon oil with a selective solvent to form rafflnate and extract phases respectively rich in paraflinic and non-paraflinic constituents and wherein the oil and solvent move countercurrently through an extraction zone, the steps comprising introducing the solvent to said zone at a point adjacent the point of rafilnate phase discharge, introducing the feed oil at a point more remote from the point of raffinate phase discharge, and maintaining the temperature in said zone at the point of oil introduction thereto 75 F. or more below the temperature at the point of solvent introduction.

BERNARD Y. MCCAR'I'Y. 

